Interpretive Summary: Fermented cucumbers occasionally spoil during long term storage. Such spoilage is characterized by the increase in pH, and formation of manure and cheese like aromas. The development of fermented cucumber spoilage causes economical losses for processors every year. This manuscript describes the development of a fermented cucumber spoilage model system, which allows for the reproduction of the event in the laboratory and will aid in the identification of strategies to prevent its development and thus economical losses for the pickling industry.

Technical Abstract:
Calcium chloride fermentations represent an alternative to reduce chloride concentrations in the wastewaters generated from commercial cucumber fermentations, currently performed in cover brine solutions containing 6% to 12% sodium chloride. However, preliminary attempts to commercially ferment the cucumbers in the presence of oxygen led to the development of a secondary cucumber fermentation or spoilage. The development of cucumber secondary fermentation has also been occasionally reported by processors using cover brine solutions containing sodium chloride. This study focused on the development of a model system to characterize calcium chloride and sodium chloride secondary cucumber fermentations under conditions similar to those present on the commercial scale. Cucumber fruits mixed with cover brine solutions, containing 100 mM calcium chloride or 1.03 M sodium chloride, and 25 mM acetic acid, were fermented in 2 L fermentation vessels subjected to air-purging at a rate of 5 mL/min. Microorganisms and selected biochemical changes detected in the experimental cucumber fermentations had been previously observed in commercial spoilage samples, suggesting the successful reproduction of the secondary fermentation in the laboratory. Experimental secondary fermentations were characterized by the rapid oxidation of the lactic acid produced during the primary fermentation, which, in turn, increased pH. Lactic acid disappearance seemed to be the result of yeast metabolism that also led to the chemical reduction of the environment to levels at which other bacteria could become established and produce butyric, propionic, and acetic acids. This model system will be applied for the identification of strategies to prevent the initiation of the cucumber secondary fermentation and reduce economic losses in the pickling industry.